Reciever.ino

#define SOLARPIN A0
#define THRESHOLD 40

void setup() {
  pinMode(SOLARPIN, INPUT);
  Serial.begin(9600);
}

void loop() {

  int reading = analogRead(SOLARPIN);
  int bits[8];
  if (reading > THRESHOLD) {
    for (int i =0; i<8 ; i++) {
      if (analogRead(SOLARPIN) > THRESHOLD) {
        bits[i] = 1 ;
      }
      else {
        bits[i] = 0;
      }
      delay(10);
    }

    int m = 0;
    for (int j =1; j <8; j++) {
    if (bits[j] ==1) {
      m = m + (1<<(7-j));
    }
    }
  
    char n=m;
    Serial.print(n);
  
  }
}